Several proteins induced under various stress conditions have been reported in many prokaryotic and eukaryotic organisms. Antibodies to some of these proteins induced in bacteria under some stress conditions have been found in the convalescent sera of patients who had those bacterial infections. We are studying the stress proteins induced in group B N. meningitidis under different stress conditions such as the lack of iron in the growth medium and lack of oxygen during growth. Our studies are focussed on a 65 kd protein induced when the bacteria is grown under stationary conditions for 72 hrs. This protein cross-reacts with monoclonal antibodies to a 63 kd protein from Bordetella pertussis which in turn cross-reacts with the GroEL protein from E. coli. The meningococcal oxygen regulated protein also reacts with polyclonal antibody against the 55K Pan1 protein of N. gonorrhoeae. We are in the process of purifying and determining the cellular localization of the protein. The elution profile of the protein on S-400 column indicates it is an oligomer with a molecular weight of over 200,000 and may be associated with outer membrane. Differences and similarities of this protein with the mycobacterial 63 kd and GroEL protein are being looked into.